Monascus spp. has been used in Chinese fermented foods for thousands of years. Red yeast rice fermented with Monascus spp. produces, in addition to some pigments, bioactive metabolites such as γ-aminobutyric acid (GABA) and polyketides monacolin K, which are used as an anti-hypertension agent (see Tsuji, K., et al., 1992, “Effects of two kinds of Koji on blood pressure in spontaneously hypertensive rats.” Nippon. Nogeikagaku Kaishi., 66: 1241-1246) and a cholesterol-lowering drug (see Endo, A., 1979, “Monacolin K, a new hypocholesterolemic agent produced by a Monascus species.” J. Antbiot., 32: 852-854; Endo, A., 1985, “Compactin (ML-236B) and related compounds as potential cholesterol-lowering agents that inhibit HMG-CoA reductase.” J. Med. Chem., 28: 401-405; and Martinokova, L., et al., 1995, “Biological activity of polyketide pigments produced by the fungus Monascus.” J. Appl. Bacteriol., 79: 609-616), respectively.
Chen, W-P. et al. (“Red mold rice prevents the development of obesity, dyslipidemia and hyperinsulinemia induced by high-fat diet.” International Journal of Obesity, 2008, 32: 1694-1704) reports that red yeast rice extracts can prevent the development of obesity, dyslipidemia and hyperinsulinemia induced by high-fat diet. The results show that water extract and ethanol extract of red yeast rice fermented by Monascus purpureus NTU 568 inhibit the proliferation of 3T3-L1 preadipocytes and inhibit the differentiation of 3T3-L1 preadipocytes to adipocytes. It is concluded that these effects probably resulted from an increase in the lipolysis activity of adipose tissue and a reduction in food/energy consumption.
The anti-diabetic effects of red yeast-fermented products were also reported (see Shi, Y. and Pan, T., J. 2010, “Anti-diabetic effects of Monascus purpureus NTU 568 fermented products on streptozotocin-induced diabetic rats.” J. Agric. Food Chem., 58(13): 7634-7640). However, the compounds in the red yeast-fermented products that have the anti-diabetic effects and their pharmacological mechanism are unknown.
Modulating lipid metabolism is one of the strategies of the treatment of metabolic syndrome. Thiazolidinediones (TZDs) are type 2 diabetes drugs developed in early 1980. Studies on mechanisms of TZDs shows that they increase insulin sensitivity by activating PPARγ. One of the characteristic effects of activating PPARγ is to increase differentiation of adipocytes. Increasing adipocyte differentiation has therefore become a popular method for screening agents that have potential in activating PPARγ and decreasing insulin resistance.